It’s best to take vyvanse no later than 12-14 hours before you expect to go to bed, but some people need longer. Try taking 500-1000mg vitamin C a couple hours before bedtime, maybe also some magnesium just before you go lay down.
The vitamin C is particularly effective in flushing out any residual vyvanse in your system to prevent it from keeping you awake, and the magnesium will help you fall asleep. Zinc-magnesium supplements are also common, and the extra zinc is needed for your body to produce dopamine (which is something that is put under stress with ADHD medication releasing so much of it).
No problem! It’s a cheap solution for me, but everyone is different ofc. As a 75kg guy who’s struggled with insomnia from birth, I can wake up way too late after losing sleep, then take my 70mg dose at 15:00 and still fall asleep by 22:00 if I take 1000mg vitamin C by 20:30
I see magnesium+zinc supplements labelled ZMA in health/fitness shops, highly recommend something like that too if you normally have trouble falling asleep anyway. It knocks me out quickly, works wonders for my sleep quality, then the next day the meds are even more effective/helpful because I got such great sleep.